Effect of testosterone and 17 beta-estradiol treatment on sex steroid binding proteins in the male of the green frog Rana esculenta

In this paper we report the effect of gonadectomy and/or long-term sex ster oid (testosterone and estradiol-17 beta) treatment and prolonged captivity (two months) on testosterone and estradiol-17 beta binding proteins (TBP an d EBP, respectively) in the plasma of the male of the green frog Rana escul enta. Experiments were carried out during different periods of the reproduc tive cycle. Gonadectomy and prolonged captivity were carried out in winter, when the spermatogenic activity slowed down and the concentration of circu lating androgens was high. Both gonadectomy and prolonged captivity resulte d in a significant decrease in TBP binding activity, which could not be res tored by the hormonal treatment, On the contrary, when the hormonal treatme nt was carried out in the early summer, when the spermatogenesis was active but the concentration of circulating androgens was low, a significant incr ease in TBP binding activity was observed. Neither gonadectomy, nor the pro longed captivity, nor the hormonal treatment affected EBP levels. Our data indicate that TBP apparent changes in response to testosterone and estradio l-17 beta treatment varied according to the period of the reproductive cycl e, an indication that studies on sex steroid binding proteins regulation sh ould take into consideration the internal endocrine condition before drawin g any final conclusion especially in species with a seasonal mode of reprod uction. (C) 2000 Elsevier Science Inc, All rights reserved.